Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C23/00—Alloys based on magnesium
  • C22C23/02—Alloys based on magnesium with aluminium as the next major constituent

Definitions

• the present invention relates to a heat-resistant magnesium alloy having excellent mechanical properties and corrosion resistance.
• Magnesium alloy is lighter than steel materials and aluminum alloys, so it is used as a lightweight substitute in various fields.
• As the magnesium alloy an AZ alloy to which Al, Mn and Zn are added and an AM alloy to which Al and Mn are added are known.
• AZ91D Mg-9 mass% Al-1 mass% Zn
• general-purpose magnesium alloys have reduced heat resistance (creep resistance) in a high temperature range of about 175 ° C., and cannot obtain heat resistance comparable to that of aluminum alloys.
• a magnesium alloy to which Ca or RE (rare earth element) is added is known as a method for improving creep resistance.
• AE44 Mg-4% mass Al-4 mass% RE having excellent creep resistance is used.
• Patent Document 1 contains 2 to 6% by weight of aluminum and 0.5 to 4% by weight of calcium as a heat-resistant magnesium alloy particularly excellent in moldability and elongation while ensuring creep resistance, and the balance is A semi-molten injection-molded magnesium alloy consisting of magnesium and unavoidable impurities and having a Ca / Al ratio of 0.8, preferably 0.6 or less has been proposed.
• Patent Document 2 when a light metal member is manufactured by semi-melt injection molding, aluminum having 2% by weight or more and 6% by weight or less and 0 as a light metal having good creep resistance and excellent forgeability. Magnesium alloys containing .5% by weight or more and 4% by weight or less of calcium have been proposed.
• the semi-melt injection molding method is a method in which a material that has been heated to be in a solid-liquid coexisting state is pressurized and injection-molded into a mold.
• Such semi-molten processing is more expensive than ordinary casting.
• quality deterioration in a low temperature environment with a high solid phase ratio becomes a problem. Specific examples of this quality deterioration include poor hot water flow and frequent poor hot water flow.
• magnesium alloys which have excellent mechanical properties including not only elongation at room temperature but also tensile strength, heat resistance represented by creep resistance, and corrosion resistance, are still in demand. Further, a magnesium alloy for casting suitable for die casting or the like, which is excellent in quality, mass productivity and cost, is desired instead of semi-melt injection molding.
• an object of the present invention is to obtain a magnesium alloy having excellent mechanical properties, heat resistance, and corrosion resistance at room temperature.
• Al is 3.0% by mass or more and less than 6.0% by mass
• Mn is 0.10% by mass or more and 0.60% by mass or less
• Ca is more than 0.50% by mass and less than 2.0% by mass
• Si is contained in an amount of more than 0.10% by mass and less than 0.40% by mass
• the balance is a magnesium alloy composed of Mg and unavoidable impurities, thereby solving the above-mentioned problems.
• magnesium alloys containing 4.5% by mass or more and less than 6.0% by mass of Al tend to exhibit more excellent mechanical properties.
• magnesium alloys containing Ca in an amount of 0.90% by mass or more and less than 2.0% by mass are likely to exhibit further excellent heat resistance.
• the magnesium alloy according to the present invention exhibits excellent mechanical properties at room temperature, heat resistance, and corrosion resistance, can improve the functions of various products, and is applied to die casting, which is excellent in mass productivity and cost. can do.
• the present invention is a magnesium alloy containing at least Al, Mn, Ca and Si.
• the magnesium alloy according to the present invention needs to have an Al content of 3.0% by mass or more, preferably 4.5% by mass or more. If the Al content is less than 3.0% by mass, the tensile strength will be too low. When the Al content is 4.5% by mass or more, it becomes easy to stably secure the tensile strength. Further, by containing Al, it is expected that the strength is improved by strengthening the solid solution and the castability is improved. Furthermore, it is expected that the heat resistance will be improved by forming a compound of Al with Ca. On the other hand, the Al content needs to be less than 6.0% by mass. If the Al content is 6.0% by mass or more, the elongation will be too low. In addition, the Mg 17 Al 12 phase may be crystallized and the heat resistance may be significantly lowered.
• the magnesium alloy according to the present invention needs to have a Mn content of 0.10% by mass or more, preferably 0.20% by mass or more.
• Mn By containing Mn, when Fe is contained as an unavoidable impurity, an Al—Fe—Mn-based compound is formed to exert an iron removal effect, and the corrosion resistance of the alloy as a whole is expected to be improved. Further, by containing Mn, finer crystal grains are expected. If the Mn content is less than 0.10% by mass, there is a high possibility that these effects cannot be sufficiently exerted.
• the Mn content needs to be 0.60% by mass or less, and preferably 0.50% by mass or less. If Mn is excessively contained in excess of 0.60% by mass, a large amount of coarse Al—Mn-based compounds are crystallized, which increases the possibility of leading to deterioration of mechanical properties.
• the magnesium alloy according to the present invention needs to have a Ca content of more than 0.50% by mass, and preferably has a Ca content of 0.90% by mass or more.
• Ca forms a compound with Al, and this compound contributes to heat resistance.
• the Al content is relatively high at 4.5% by mass or more, a sufficient amount of the intermetallic compound is formed, so that the Ca content is preferably 0.90% by mass or more.
• the Ca content needs to be less than 2.0% by mass, preferably 1.8% by mass or less.
• the tensile strength and elongation are likely to cause a problem in corrosion resistance. Further, if Ca is contained in an excessive amount, cracks may occur during casting and the seizure property may be deteriorated.
• the magnesium alloy according to the present invention needs to have a Si content of more than 0.10% by mass.
• Si forms an Mg-Ca-Si compound with Ca and is expected to improve heat resistance, but if the content is less than 0.10% by mass, this effect is not sufficiently exhibited.
• the Si content needs to be less than 0.40% by mass. If Si is excessively contained, the Mg—Ca—Si compound is coarsely crystallized, and there is a high possibility that the toughness is lowered.
• the magnesium alloy according to the present invention may contain unavoidable impurities in addition to the above elements.
• This unavoidable impurity is unavoidably contained unintentionally due to a manufacturing problem or a raw material problem.
• elements such as Ti, Cr, Fe, Ni, Cu, Sr, Zr, Be, Ba, and RE (rare earth elements) can be mentioned.
• Each element needs to have a content within a range that does not impair the characteristics of the magnesium alloy according to the present invention, preferably less than 0.1% by mass per element, preferably less, and below the detection limit. It is particularly preferable to have it.
• the total content of unavoidable impurities is preferably less than 0.5% by mass, more preferably less than 0.2% by mass, further preferably less than 0.1% by mass, and below the detection limit. It is particularly preferable to have it.
• the magnesium alloy according to the present invention can be prepared by a general method using a raw material containing the above elements so as to be in the range of the above mass%.
• the above mass% is not a value in the raw material, but a value in the prepared alloy or a product manufactured by casting the alloy.
• the magnesium alloy according to the present invention has excellent tensile strength and elongation at room temperature, as well as heat resistance typified by creep resistance, and also excellent corrosion resistance.
• it can be used for production in the same procedure as a general-purpose material of magnesium alloy, and can be particularly preferably used in applications where excellent mechanical properties, excellent heat resistance, and excellent corrosion resistance at room temperature are required. Therefore, a cast structural material having excellent mechanical properties, heat resistance, and corrosion resistance can be obtained by die casting, which is excellent in mass productivity and cost, instead of semi-melt injection molding.
• a magnesium alloy was prepared so that the content of elements other than Mg was the mass% shown in each of Table 1 below, and the test required for the preparation of the d "tensile test piece" of JIS H 5203 "8.
• An alloy material was prepared based on "collection of material” (corresponding to ISO16220-5). That is, a sample material was collected from a magnesium alloy adjusted to have a mass% of the mass% shown in each of Table 1 by a gravity casting method. Elements other than those listed were below the detection limit.
• Each alloy was tested based on the tensile test method specified in JIS Z 2241 (corresponding to ISO6892-1).
• the test piece was prepared by machining the above-mentioned alloy material, and the tensile strength and elongation were measured using a universal testing machine (manufactured by Shimadzu Corporation: UH-500kNX).
• test was conducted based on the creep test method specified in JIS Z 2271 (corresponding to ISO204: 2009).
• the test piece was manufactured by machining the above alloy material, and the creep tester was manufactured by Shinko Kagaku Kikai Co., Ltd .: SK-3, the test temperature was 175 ° C, and the applied stress was 50 MPa. The creep strain (%) after 100 hours was measured.
• test was conducted based on the salt spray test method specified in JIS Z 2371 (corresponding to ISO9227: 2012).
• the test piece was formed by gravity casting and then machined.
• a test machine manufactured by Suga Test Instruments Co., Ltd. was used, the test method was a neutral salt spray test, and the test time was 96 hours.
• the mixture was boiled in a mixed aqueous solution of chromium (VI) oxide and silver nitrate for 1 minute to remove corrosion products, and the corrosion weight loss was measured.
• VI chromium
• Table 1 below shows the tensile strength, elongation, creep strain and comprehensive evaluation, as well as the component ratio of each test piece.
• the evaluation is “B” Bad, “G” Good, and “VG” Very Good from the worst.
• the tensile strength was evaluated as “B” for less than 150 MPa, “G” for 150 MPa or more and less than 170 MPa, and “VG” for 170 MPa or more.
• the growth was evaluated as “B” for less than 3.5%, “G” for 3.5% or more and less than 4.0%, and "VG” for 4.0% or more.
• the creep strain was evaluated as “B” for more than 0.25%, "G” for more than 0.18% and 0.25% or less, and "VG” for 0.18% or less.
• Comparative Example 1 In Comparative Example 1 in which the Al content was insufficient, both tensile strength and elongation were insufficient. On the other hand, in Comparative Example 2 and Comparative Example 6 in which the Al content was excessive, the elongation deteriorated. Comparative Examples 3 and 5 in which the Ca content was excessive caused problems in both elongation and tensile strength. Comparative Examples 4 and 5 in which the Si content was excessive also had problems in elongation and tensile strength.
• Table 2 below shows the corrosion weight loss along with the component ratio of each test piece.
• Examples 12 to 15 showed good corrosion resistance of less than 5.00 mcd (mg / cm 2 / day). However, Comparative Example 7 had a corrosion resistance of 5.11 mcd, which was not sufficient. It is considered that the corrosion resistance deteriorated because the Ca content was excessive.

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• 2020
  • 2020-03-06 EP EP20784289.9A patent/EP3950988A4/de active Pending
  • 2020-03-06 WO PCT/JP2020/009662 patent/WO2020203041A1/ja unknown
  • 2020-03-06 JP JP2021511296A patent/JP7475330B2/ja active Active
  • 2020-03-06 US US17/599,665 patent/US11959155B2/en active Active

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